Electron discharge device utilizing cavity resonators



March 21, 1950 L. s. NERGAARD ELECTRON DISCHARGE DEVICE UTILIZING CAVITY RESONATORS 3 Sheets-Sheet l if 5. (7777/0175 P0772. TFNK Original Filed Dec. 31; 1945 Knucntor LEEIN 5.NERBHHRD 9 g 4% W (Yttorncg TILIZING 5 Sheets-Sheet 2 NERGAARD N \N N L. S. ELECTRON DISCHARGE DEVICE U CAVITY RESONATORS March 21, 1950 Original Filed Dec. 31, 1943 '31! cnfor LEDN SNEREHHRD GHOHIQU March 21, 1950 L. s. NERGAARD ELECTRON DISCHARGE DEVI G N I Z I L I W m E O C T A N O S E R Y T W A C Oiiginal Filed Dec.

3 Sheets-Sheet 5 lnvcntox D m R M H w H G Patented Mar. 21, 1950 ELECTRON DISCHARGE DEVICE UTILIZING CAVITY RESONATORS Leon S. Nergaard, Princeton, N.

J assignor to Radio Corporation of America, a corporation of Delaware Original application December 31, 1943, Serial No. 516,388. Divided and this application May 25, 1948, Serial No. 29,034

2 Claims.

My invention relates to electron discharge devices and associated circuits, more particularly to such devices useful at very high frequencies.

This application is a division of my copending application Serial No. 516,388, filed December 31, 1943, now Patent No. 2,461,125, dated February 8, 19 :9, and assigned to the same assignee as the present application.

An object of my invention is to provide an electron discharge device and associated circuit particularly suitable for high frequency operation and capable of delivering large amounts of power.

Another object of my invention is to provide an electron discharge device which can deliver large amounts of power at high frequencies, but which is nevertheless small and compact, has few parts, and lends itself readily to manufacture.

A further object of my invention is to provide such a device having a low internal reactance which permits the use of a larger external circuit, that is, a device which will function at higher frequencies with an external circuit and thus permit tuning over a considerable range.

A more specific object of my invention is to provide an electron discharge device in which the electrodes although closely spaced are firmly and rigidly supported with respect to each other.

Another specific object of my invention is to provide an electron discharge device in which the anode forms part of the tube envelope and in which the anode-to-envelope seal is protected against electron bombardment.

A further object of my invention is to provide an electron discharge device having electrode leads and supports which will merge into high frequency circuits of the cavity resonator type so that the internal reactances may be coupled smoothly to the external reactances which complete the circuit and thus reduce radio frequency losses and spurious modes of oscillation to a minimum.

Another specific object of my invention is to provide an electron discharge device having a cathode support and lead and a cooperating protecting sleeve which also acts as a cathode terminal permitting ready connection to a transmission line and reception of the electron discharge device in any angular position in a circuit.

A further object of my invention is to provide a terminal and shield for the cathode lead which facilitates incorporation of the electron discharge device into a cavity resonator circuit of the coaxial line type.

Another specific object of my invention is to provide a cathode which will promote heater power economy.

A still further object of my invention is to provide a lead and support for the cathode of an electron discharge device of the type described, which reduces the number of leads for the cathode, lowers the radio frequency losses, reduces the number of parts required and makes possible the use of a simple tip-off after exhaust.

A further object of my invention is to provide an electron discharge device and associated circuit having an improved coupling loop for providing feedback when the device is to act as an oscillator.

A further object of my invention is to provide a cavity resonator circuit in which the circuit has large dimensions while permitting operation at very high frequencies.

Another object of my invention is to provide an electron discharge device and associated circuits comprising cavity resonators which provide a novel method of introducing biasing voltages on the electrodes enclosed within the cavity resonators.

A still further object of my invention is to provide a load coupling system which eliminates large grid swings upon removal of the load thus reducing chances of injury to the grid electrode,

A further object of my invention is to provide improved means for connecting the terminals of an electron discharge device to a cavity resonator circuit.

Another object of my invention is to provide a tuning condenser of improved design for a cavity resonator circuit.

These and other objects will appear hereinafter.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims, but the invention itself will best be understood by reference to the following description taken in connection with the accompanying drawing in which Fig. l is a longitudinal section of an electron discharge device and associated circuit made according to my invention, Fig. 2 is a partial longitudinal section taken along the line IIII of Fig. 1, Fig. 3 is an equivalent circuit diagram of circuits utilizing the apparatus shown in Fig. 1, Fig. 4 is an enlarged longitudinal section of an electron discharge device utilizing the apparatus shown in Fig. 1, Fig. 5 is a schematic diagram of the ultra high frequency apparatus made accordin to my invention and shown in Fig. 1, Fig. 6 is a longitudinal section of a modification of the ultra high 3 frequency apparatus shown in Fig. 1. Fig. 7 is a transverse sectional detail utilized in Fig. 6. and Fig. 8 is a section taken along the line VIII-VIII of Fig. 1.

The ultra high frequency apparatus made according to my invention and shown in Fig. 1 con-- sists of a specially designed triode electron discharge device specially adapted and designed to cooperate with cavity resonator type circuits. Briefly the electron discharge device comprises essentially a cathode, grid and anode of the coaxial type, the anode forming part of the tube envelope. The grid and cathode are provided with specially designed terminals cooperating with and merging into the circuits proper. Connected between the grid and cathode is a coaxial line type resonator which provides the input circuit and coupled between the anode and grid is another coaxial line resonator of the half-wave open line type which provides the output circuit. The input resonator is tuned by means of a specially designed tuning condenser and energy is taken from the input circuit. A specially designed coupling loop couples the input and output resonators and is provided with means for tuning the loop to increase the efiiciency of operation. In accordance with my invention high voltage is applied to the anode by means of a novel type probe.

The electron discharge device per se will be de scribed before the apparatus as a whole. Referring to Fig. 4- an electron discharge device made according to my invention includes the inverted cup-shaped cathode lli provided with the heater H. A cup-shaped grid comprising a cap I? and grid wires l2 encloses the cathode and is coaxial therewith. An inverted cup-shaped anode l3, preferably formed from a copper block, encloses the cathode and grid and is coaxial with the latter two electrodes. For cooling purposes radiating fins are fastened, preferably by cadmium soldering to the anode block.

The grid is'supported on a cone-shaped supporting member l5 secured to the collar it, which is provided with oppositely directed flanges Hi" and I6". The anode is provided with a ring-like sealing member l! of inverted U-shaped transverse section. Sealed between the outer leg of the member I? and the flange it is the insulating collar l8 preferably of glass. The cathode is supported on a tubular member iii by means of the fingers sealed between the cup-shaped member l0 and the closure member 2! of the cathode. Th'ese'fingers reduce the heat conduction from the cathode to the cathode support H3, at the same time providing rigid support for maintaining proper spacing between the cathode and grid. One end of the cathode heater ii is electrically connected to the cathode cup iii and the other provided with a lead 22 sealed through the end of the tubular member If! by insulating seal 23. The tubular member it is in turn hermetically sealed to the flange It" by means of seal 24 of insulating material, preferably glass. The collar I6 is in turn provided with a radially extending transverse flange 25 for purposes to be described. A getter element 26 is connected between the tubular member I!) and the lead 25 sealed through the end of the tubular member H3 at 27. Thus the grid and cathode are hermetically sealed within a vacuum-tight space which may be evacuated through the sealed off tubulation 28.

The grid and cathode may be assembled as a unit after which the anode may be sealed to the grid collar it by means of collar l8. Because the cathode is cylindrical, greater heater power economy results, and because of the support of the cathode from the cathode cylinder [9, heat losses are reduced. Because of the cone support, great lateral stability of the grid results and a reduction in cathode-tmgrid capacity results. Further stability is insured by the use of the element i i extending through the top of the grid but insulated therefrom by means of the tubular member 3d. The element ll also supports the element 29 which may be utilized to increase the cathode-anode capacity for feedback purposes if desired. Element 29 could also be eliminated and all of the desired feedback obtained in a manner to be described. Because of the cathode and grid supports by means of the cone and tubular member l9, lower radio frequency losses occur and the result in mechanical assembly becomes quite simple. This construction also reduces the number of parts necessary for the assembly. The use of the cylindrical cathode lead it reduces the need for a great many leads through a glass stem and press and results in considerably less loss of radio frequency power. It also reduces the number of parts necessary for a cathode assembly and permits the use of a copper tip-oif if desired.

The cathode cylinder is extended with a copper thimble or elongated cup-shaped member 3|. This member slides over and is secured to the cathode support I9 and is provided with slots 32 and 33 for receiving the seals 2'i23. The

heater lead 22 is extended by means of the conductor 36 to the jack pin 34 insulated from member Si by means of insulator collar 35. This thimble results in the protection of the exhaust tubulation and heater and getter leads, provides a cathode terminal which can be plugged into an appropriate socket in the transmission line and brings the heater lead out on the axis of symmetry so that the tube can be plugged into the circuit without reference to its angular position.

The assembled high frequency apparatus for generating an ultra high frequency power output and utilizing an electron discharge device of the type shown in Fig. 4, is shown in Fig. 1. The input circuit is of the coaxial line cavity resonator type coupled between the grid and the cathode, the end removed from the grid and cathode being closed.

This circuit comprises an outer tubular member 40 and inner tubular member 4| electrically connected together and closed by means of the conducting disc 42. Transverse disc 43 is electrically and mechanically secured to the tubular member 40 and is provided with a shoulder or shelf 44 as shown in Figs. 1 and 8 for receiving the grid ring 25 of the tube.

As best shown in Fig. 8, supported on the member 43 are aplurality of sliding clamps'45, 46, ll and 43 which can be slid transversely of the longitudinal axis of the electron discharge device to secure the grid ring to this member. They are slidably retained by means of the screw elements 49 which can be tightened when the grid ring is in place. Thus there is a direct electrical connection between the outside tubular member iii and the grid, permitting thegridto be operated at ground potential. This arrangement also gives good thermal contact to the gridflange, thus reducing the grid temperature. The cathode is capacitively coupled to the inner tubular member. Mounted within the inner tubular member 4| is the tubular member 50, preferably of mica and a second tubular member 5|, which is conducting and provided with a cup-shaped portion 54 having spring fingers 52 thereon engaging the outer surfaces of the cathode thimble 3|. This arrangement capacitlvely couples the cathode to the inner tubular member.

The cathode heater is supplied by means of the conductors 55 and 56. The conductor 55 is electrically connected to inner tubular member 5| in turn providing a circuit to one side of the cathode heater through fingers 52, cathode thimble 3|, cathode lead and support l9, to the ribbon-like supports 20, to one side of the cathode, back through the cathode heater conductor 22, conductor 36, pin 34', jack 53, which is insulatingly supported by insulation 54' within the cup-shaped member 54.

The tank circuit coupled between the grid and the anode is of the coaxial half wave open line type and includes the inner tubular member 59 of cup-shape and secured to the anode radiator by means of screw 6| and provided with curved-in lip 60 for reducing corona losses. The outer tubular member 59 is mechanically and electrically secured to the grid support 43. The member 59 extends beyond the end of member 60 to prevent radiation from the open end of the line. The cylinder 59 can be closed at its open end provided the closure is made about a diameter of 60 from the end of 60. This provides a half wave cavity resonator and because of its arrangement it can be made larger than the closed type and thus reduces the possibility of serious voltage breakdown problems which would occur with small size cavity resonators maintained to operate, for example, at frequencies higher than 600 megacycles.

While the apparatus could be operated as an amplifier, I prefer to utilize it as an oscillator and for this purpose I provide the member 43 with an aperture 43 to permit the use of a coupling loop consisting of tubular element 10 and tubular element 1|, in which is telescopically supported the U-shaped member 12, the length of which can be varied to determine the amount of coupling desired. The portion of the element 1| within the anode tank circuit is formed as shown at 13 to reduce sharp corners and remove the loop as far as possible from the high voltage field of the anode.

In order to tune out the reactance of the coupling loops I provide a tuning stub consisting of the inner conductor I4 and the outer tubular member 15 with a tuning ring 16 operated by means of the operating handle 11. This increases the power output and efficiency considerably. The equivalent electrical circuit of the coupling loop and tuning stub and the relationship to the circuit is shown in Fig. 3, the same numerals being utilized to indicate the same elements shown in Fig. 1. This tuning stub is not part of my invention but is described and claimed in a copending application of Robert P. Stone, Serial No. 547,190, filed July 29, 1944, and assigned to the same assignee as the present invention.

In order to tune the input circuit, I provide a tuning condenser 62 in the form of a disc or plate having a rounded periphery in order to avoid sharp edges in the high frequency field. This eliminates the corona which is experienced whenever sharp edges are used between elements at high frequency potential differences. This tuning condenser plate is slidable along the inner tubular member 4| and is operated by a type.

gear boxmechanism indicated generally at 63. A shaft 64 is rotated by means of knob 65 which in turn rotates a gear 64' coupled to the gears 66' and 61 for rotating shafts 68 and 69 threadably engaged with the tuning condenser 62 shown in Fig. 2. The shaft is mounted on bearings 65' and 65". Rotation of the knob 55 moves the tuning condenser along the inner member for tuning the input circuit. This tuning condenser also shortens the line and makes the circuit more compact.

The anode voltage is brought to the anode l3 by means of a probe which lies along a direct current line of force and along a radio frequency nodal line. This probe minimizes voltage breakdown possibilities and prevents radio frequency energy from being picked up by the lead. It consists of a. conducting tubular member having insulating sleeve 8| and supporting a conducting lead 82 at the inner end of whichis spring 38, biasing the probe point 48 into contact with the anode radiator I4. I

The output is taken from the input resonator by means of the coaxial load line 51-53, the

inner conductor 51 contacting tubular member 4| of the input resonator.

In order to cool the radiator and the seals of the electron discharge device, a slot 59' is provided in the outer conductor 59.

Fig. 5 is a schematic diagram showing the voltage sources and the method of applying a pulse voltage to the anode for controlling oscillation of the apparatus made according to my invention. For the cathode heater I provide a ;transformer 84 which is electrically connected to the cathode heater leads. The cavity resonators are grounded by means of the conductor 85 and bias between the cathode and grid obtained by means of biasing resistors 86 which are variable. The plate voltage which may be a, steady D. C. voltage or pulse voltage is applied through the transformer 81.

In Fig. 6 is shown a modification of the ultra high frequency apparatus shown in Fig. 1 and utilizing the electron discharge device shown in Fig. 4. Like numerals indicate like parts in Figs. 1, 4, 6 and 8.

The cavity resonator circuit connected between the cathode and grid is again of the coaxial line means of sliding clamps 48' to a member 90 closing one end of the coaxial line circuit coupled between the cathode and grid, this circuit comprising the outer tubular member 40 and the inner tubular member 4|, the. inner cathode heater lead pin 34 being received within a jack insulatingly supported by means of the insulating support member 54. Tuning of the input circuit is accomplished by means of the shorting ring 62 operated by means of handles 68' and 69, the cathode heater current being supplied by means of leads 55-56 in the same manner as shown in Fig. l. The output resonator includes the apertured plate member 90 and ring member 94 and the collar 92 providing a cavity resonator of drum shape. An anode flange I3 is clamped to the top electrode of the plate condenser. The plate condenser is positioned between the member 92 and the plate flange l3 and comprises the two electrodes 93 and 94 separated by the member 9 of mica. The member 9|] may comprise mica discs having graded annular rings of silver to distribute the electric field uniformly and may be coated with a thin layer of titanium oxide salve to eliminate spark- The grid ring 25 is again clamped by.

ing and burning between sheets. Fillets of titanium :oxide salve aremade around theedges of the electrodes to eliminat .corona in the soondenser.

The output is taken from the tankby means of the coupling loop.95 formingthe inner conductor of the coaxial output line, the outerconductor .of which is .tubular .member 96.

In accordance with myinvention feedback is obtained by tapping a line 91' on .to the .output line 95 through a slot in the outer conductor .96 of the output line. The feedback line is carried in .:a channel 99 to prevent radiation down to an appropriate place on the cathode line. Here it :is connected to slide tap 98 on the cathode line through a slot 40" in'the outer conductor 40'. Feedback is .varied bysliding the tap.

The feedback :is takenon the output line side of the coupling loop. The usual feedback :systems .are such that if a load is removed :from theoscillator the grid swing increases. In many cases this swing increase is sufficient to .injure the grid. This is particularly apt to happen whenmaking adjustments of load coupling. If feedback is taken from the output line on the load side of the load coupling'adjusting means, this difficulty is completely eliminated. Then when the load coupling is decreased the feedback also decreases and the grid swing is reduced instead of increased as in the usual arrangements. The arrangement described was found by actual test to be most satisfactory.

The anode is cooled by an air blast on the radiator, which is one of the fittings on the tube.

The member 9'2 is provided with tubular member l extending therethrough and provided with apertures, such as It! and I02 as shown in Fig. .7. Theglass work within the output cavity resonator is cooled by air jets diametrically opposite the output system. Four jets may be applied, one pair to direct cool air to flow on the glass-tometal seals and the other pair to provide a flow of air around the glass work withoutstriking it directly. This is desirable where the air lines contain moisture or oil which mightcrack hot glass if blown directly upon it. The cathode-togridiglass work is cooled'by anair jet in the cover for the channel in which the feedback line .lles. Apparatus of the type describedabove is operatedsuccessfully at .600 megacycles with over'lilO kilowatt output when pulse-operated. Also 300 watts continuous wave with D. C. applied.

All of the features pointed out above as desirable have .been included in the apparatus made according to my invention and described above.

While I have indicated the preferred embodiments of my invention of which I am now aware and have'also indicated only one specific application for which my invention may be employed, it willbeapparent that my invention is by no means limited to the exact forms illustrated or the use indicated, but that many variationsmay be made in :the particular structure used and the 'purpose for which it is employed without departing :from the scope of my invention as set forth in :the appended claims.

I claim:

'1. .An electron discharge device having a cathode,grid and an anode, said grid beingprovided with a radially extending flange, and a flange on said anode, said-cathode beingprovided witha tubular lead and terminal, a cavity :resonatorscoupledbetween the anode andgrid, and means clamping said flanges to said resonator, and a coupling .loop within said resonator, a coaxial line connected to andextendingirom said coupling loop and adapted to be coupled to a lead, a cavity resonator coupled between said grid and said cathode and including acoaxial line comprising an outer conductor-and an inner conductor, the inner conductor being capacity coupled to said tubular cathode lead,-a coupling member supported by and electrically connected to the inner conductor of the coaxial lineresonator and aieedback line connectedbetween said coupling member and the coaxial line connected tosaid coupling loop.

2. An electron discharge device having a cathode, grid and an anode, said grid being provided with a radially extending flange, and a flange on said anode-said cathode being provided with a tubular lead andlterminal, a cavityresonator coupled between the anode and grid, and means clamping said xfianges to said resonator, and .a coupling .loop within said resonator, a coaxial line connected to and extendingirom said coupling loop and adapted to be coupled to a load, a coaxial line cavity resonator coupled'between said gridand said cathode and. comprising an outer conductor and an inner conductonthe inner conductor being capacity coupled to said tubular cathode lead, a coupling member slidable on said inner conductor of said .coaxial line resonatorand a.feedback.line connected between said couplinglmember and the coaxiallinecom nected .to saidicoupling loop and having slidable contact with said coupling member, and means coupledto said anode-grid resonator for injecting a cooling medium into said anode-grid resonator.

LEON. S. NERGAARD.

REFERENCES CITED The following references are of record in the file of this "patent:

UNITED STATES PATENTS Number Name :Date

2,304,186 Litton Dec. 8,?1942 2,400,753 II-Iaeif May 21,1946 2,438,768 .Stewart Mar. 30, 1948 12,445,077 Nergaard et al July 13, 1948 

